1. Field of the Invention
The present invention relates to an apparatus, a system, and a method to efficiently report ACKs/NAKs for a centralized scheduler wireless system that uses tunneling for data transmission and, in order to reduce a usage of bandwidth for reporting, the apparatus, the system, and the method perform an aggregation via coding of ACK/NAK channels.
2. Description of the Related Art
A worldwide interoperability for microwave access (WiMAX) system lends itself as a lightweight Internet access technology. It is built on top of 802.16 standard family MAC+PHY (Medium Access Control+Physical layer) standard from IEEE (certified by WiMAX). The system standard (higher layers and network) is standardized and certified by WiMAX Forum.
802.16 Mobile Multi-Hop Relay (MMR), a study item established in the IEEE 802.16 working group, provides examples of relay networking. The MMR working group focuses on defining a network system that utilizes relays stations (RS) to extend the network coverage and/or enhance the system throughput. A relay network may include, in part, relay stations (RS0 and RS1), mobile stations or subscriber stations (MS0, MS1, and MS2), and a base station (BS).
Hybrid automatic repeat request (H-ARQ) is a scheme which combines ARQ protocols with forward-error-correcting (FEC) schemes that are generally considered to be the best error-control techniques for wireless links. Different wireless technology may have different H-ARQ schemes.
In IEEE 802.16, the H-ARQ scheme is implemented as a part of the media access controller (MAC) and can be enabled on a per-terminal basis. Two main variants of H-ARQ are supported: chase combining and incremental redundancy (IR). For Internet protocol detailed recorder (IR), the PHY layer encodes the H-ARQ generating four versions for the encoded H-ARQ attempts. Each H-ARQ attempt is uniquely identified using a H-ARQ attempt identifier (SPID). For chase combining, the PHY layer encodes the H-ARQ packet generating only one version of the encoded packet. As a result, no SPID is required for chase combining.
For downlink operation, the BS sends a version of the encoded H-ARQ packet to the MS. The MS attempts to decode the encoded packet on this first H-ARQ attempt. If the decoding is successful, the MS sends an acknowledgement (ACK) to the BS. If the decoding is not successful, the MS sends a non-acknowledgement (NAK) to the BS. In response, the BS will send another H-ARQ attempt to the MS. The BS may continue to send H-ARQ attempts until the MS successfully decodes the packet and sends an ACK.
The H-ARQ scheme works well in a system without a relay station (RS) where the H-ARQ scheme is applied directly between the BS and MS. However, when a RS is introduced into the system, although H-ARQ is still implemented between the MS and BS, the RS needs to forward all the H-ARQ attempts and ACK/NAKs between the MS and BS.
Therefore, according to conventional solutions, if the first H-ARQ attempt is not sent successfully due to error or loss, another H-ARQ attempt needs to be sent until a mobile station (MS) or base station (BS) successfully decodes it. Consequently, the subsequent H-ARQ attempt(s) must be transmitted over all the different hops (links) between the BS and the MS. Bandwidth is re-allocated between BS and MS for transmitting the subsequent H-ARQ attempt(s), even though some of the links may have already transferred the frame successfully. This results in bandwidth wastage and throughput loss. Thus, there is a need for an enhanced H-ARQ scheme with an improved utilization of network resources.
In view of the above, an apparatus, a system, and a method are needed that would provide an efficient mode to report ACKs/NAKs for a centralized scheduler wireless system that uses tunneling for data transmission.